@mixin bg-img($url) {
  background-image: url($url + '.png');
  background-repeat:no-repeat;
  background-size:100% 100%;
  -moz-background-size:100% 100%;
  @media (-webkit-min-device-pixel-ratio: 2), (min-device-pixel-ratio: 2) {
    background-image: url($url + '@2x.png');
    background-repeat:no-repeat;
    background-size:100% 100%;
    -moz-background-size:100% 100%;
  }
  @media (-webkit-min-device-pixel-ratio: 3), (min-device-pixel-ratio: 3) {
    background-image: url($url + '@3x.png');
    background-repeat:no-repeat;
    background-size:100% 100%;
    -moz-background-size:100% 100%;
  }
}

@mixin bg-img-auto($url) {
  background-image: url($url + '.png');
  @media (-webkit-min-device-pixel-ratio: 2), (min-device-pixel-ratio: 2) {
    background-image: url($url + '@2x.png');
  }
  @media (-webkit-min-device-pixel-ratio: 3), (min-device-pixel-ratio: 3) {
    background-image: url($url + '@3x.png');
  }
}

@mixin border-1px($color) {
  position: relative;
  &:after {
    display: block;
    position: absolute;
    left: 0;
    bottom: 0;
    width: 100%;
    border-top: 1px solid $color;
    content: ' ';
  }
}